1. Field of the Invention
The present invention relates to a device for holding, adjusting and driving a rotatable body such as a polygonal mirror useful in devices such as a nonmechanical printer.
2. Description of the Prior Art
German Patent Specification No. 27 17 299 and its corresponding U.S. Pat. No. 4,147,401 along with its French Pat. No. 2,388,291 all describe a rotatable polygonal mirror which is connected to an axis of rotation by use of an adjusting disc having a plurality of set screws. The adjusting disc is rigidly attached to the axis of rotation, i.e. the drive shaft. The polygonal mirror is pressed against the set screws of the adjusting disc using a resilient element so that the mirror can be positioned relative to the axis of rotation by means of the set screws.
This device has the drawback that the required positioning is obtained against the action of a certain spring force, so that precise positioning may be disturbed upon rotation of the body (certainly at high speeds). Additionally, the drive torque of the axis of rotation is transmitted to the rotatable body through a resilient element possibly resulting in a difference between the rotational speed of the axis of rotation and the rotational speed of the rotatable body.
U.S. Pat. No. 4,141,620 describes another device for holding and adjusting a polygon mirror. This device, however, uses an air bearing and requires that the polygon mirror be enclosed within the air bearing. Also, the polygon mirror is resiliently fixed to the drive shaft.
U.S. Pat. No. 2,010,411 and German Pat. No. 639,296 disclose devices for holding and adjusting mirror wheels which utilize a disc to hold and adjust them. These devices suffer from the same disadvantages as the device described in U.S. Pat. No. 4,147,401. Similarly, Japanese Abstract 59-30513 entitled Rotary Polyhedral Mirror Body only describes a way to prevent deviations in the plane of rotation of a polyhedral mirror caused by fastening the mirror to the axis of rotation by means of a set screw and does not solve the disadvantages discussed above.